Objective-C iOS 从 Torrent 文件生成 Info_Hash

Question

我目前正在努力尝试从我下载的 torrent 文件中生成 info_hash。我使用 uTorrent 创建了 Torrent 文件，并使用 PeerTracker 作为我的跟踪软件。

我使用的是此处代码的更新版本：
https://code.google.com/p/rouge-server/source/browse/trunk/driver/objective-c/RougeDriver/BEncoding.m?r=88

{
    announce = "http://sub.url.com:8080/announce.php";
    "created by" = "uTorrent/1870";
    "creation date" = 1425134140;
    encoding = "UTF-8";
    info =     {
        length = 4;
        name = "test.txt";
        "piece length" = 16384;
        pieces = "\U00a9J\U00e8\U00c2\U00c3\U00b1\U00f5\U00b6L\bs\U201d\U00eb\U00c8\U00e1\U00f2/\U00aa\U201d";
    };
}

下面是我使用的确切编码方法：

+ (void)encode:(id)object toString:(NSMutableString *)string
{
    if([object isKindOfClass:[NSDictionary class]])
    {
        NSDictionary *dictionary = (NSDictionary *)object;
        [string appendString:@"d"];

        for(id key in [dictionary allKeys])
        {
            [self encode:key toString:string];
            [self encode:[dictionary objectForKey:key] toString:string];
        }

        [string appendString:@"e"];
    }
    else if([object isKindOfClass:[NSString class]])
    {
        NSString *stringObject = (NSString *)object;
        NSString *format = @"%lu:%@";

        [string appendFormat:format, [string length], stringObject];
    }
    else if([object isKindOfClass:[NSArray class]])
    {
        NSArray *array = (NSArray *)object;
        [string appendString:@"l"];

        for(id item in array)
        {
            [self encode:item toString:string];
        }

        [string appendString:@"e"];
    }
    else if([object isKindOfClass:[NSNumber class]])
    {
        NSNumber *number = (NSNumber *)object;
        NSString *format = @"i%de";

        [string appendFormat:format, [number intValue]];
    }
}

这是我第一次使用 Torrents 和编码。我知道我只应该对主词典中包含的 "info" 词典进行编码。

有谁知道我这里可能哪里出错了？

Answer 1

实际pieces内容是数据：

0xa9, 0x4a, 0x8f, 0xe5, 0xcc, 0xb1, 0x9b, 0xa6, 0x1c, 0x4c, 0x08, 0x73, 0xd3, 0x91, 0xe9, 0x87, 0x98, 0x2f, 0xbb, 0xd3

如@Encombe 所述，这是 SHA1 哈希。

来自维基百科：

The specification does not deal with encoding of characters outside the ASCII set; to mitigate this, some BitTorrent applications explicitly communicate the encoding (most commonly UTF-8) in various non-standard ways.

而pieces是十六进制数据，不是UTF-8。

Answer 2

我终于找到了解决这个问题的方法。大家都怀疑是编码问题。

我按照此 SO 中的说明进行操作： Calculating the info-hash of a torrent file

不过，我做了一个小调整：

+ (NSDictionary *)decodeDictionary:(HTData *)data
{
    NSMutableDictionary *dictionary = [NSMutableDictionary dictionary];

    [data getNextCharacter];

    while([data showNextCharacter] != 'e')
    {
        NSString *key = [self decodeString:data];

        id object;

        if([key isEqualToString:@"info"])
        {
            NSInteger startIndex = [data getCurrentIndex];
            NSInteger endIndex;
            object = [self decodeNextObject:data];

            endIndex = [data getCurrentIndex];

            NSMutableData *charData = [[NSMutableData alloc] init];

            for(NSInteger i = startIndex; i < endIndex; i++)
            {
                char c = [data charAtIndex:i];
                [charData appendBytes:&c length:1];
            }

            NSData *hashedInfo = [charData SHA1];

            [dictionary setObject:hashedInfo forKey:@"info_hash"];
        }
        else
        {
            object = [self decodeNextObject:data];
        }

        [dictionary setObject:object forKey:key];
    }

    [data getNextCharacter];

    return dictionary;
 }

我现在正在计算字典解码器中的哈希值。我还在处理个人 chars 并将它们直接附加到 NSMutableData 对象。这避免了我遇到的编码问题并生成正确的散列。

不是最优雅的解决方案，但我很高兴它有效。

Objective-C iOS 从 Torrent 文件生成 Info_Hash

Objective-C iOS Generating Info_Hash from Torrent File

ios

objective-c

torrent